There are, at the present time, a wide variety of commercially available devices within the field of the invention and the capability of these devices is truly remarkable. They can be characterized as including a keyboard with a plurality of keys thereon (similar to a typewriter). Depression of one or a combination of keys generates a unique coded signal (or keycode) which has the effect of providing a particular graphic or executing a function (such as carrier return, tab, etc.) with corresponding code storage; the keyboard forms one of the two major input capabilities. The other input capability is provided by a device for reading/recording on replaceable media; typically today, that media is magnetic, in the form of a card, tape or disc. Devices within the field of the invention also include some type of printing arrangement for printing with an impact, ink jet or other printer, a document including multiple lines of text in operator selected format; typically the document is the final desired product. Another output capability is provided by the display (usually an electronic display such as a cathode ray tube) which is capable of displaying a visible image made up of multiple lines each with multiple character locations. Responding to the input devices and controlling the output devices, is typically a microcomputer (although mini-computers and even main frame computers can also be used).
Notwithstanding the truly remarkable capability of devices currently available, there is a desire for further improvement. One very important area in which improvement can be obtained is that relating to the electronic display where a number of trade-offs have been made in the past. Some devices have what is termed "full page" display capability in that the electronic display is capable of displaying up to 66 lines of text (which can be considered to constitute an entire page). Since it is the purpose of the electronic display to enable the operator to preview what the printer would produce if it were initiated into action, it was believed essential that the operator be able to distinguish, on the electronic display, all the various characters which the printer is capable of producing. This implies a certain minimal level of visible resolution. This resolution requirement coupled with the capability of displaying up to 66 lines of text, each line including generally 80 to 100 characters or more, dictates size of the electronic display, and this size carries with it cost and space requirements that it is one objective of the invention to improve. Other devices within the field of the invention include electronic displays which are incapable of displaying a so-called full page of text, and typically these electronic displays produce a visible image consisting of from 6 to about 30 lines of text. Obviously, with this reduced requirement, the size of the electronic display can be relaxed without sacrificing resolution. Since, however, this electronic display does not produce an image corresponding to an entire "page" it is impossible for the operator to accurately preview the appearance of an entire page.
The prior art does illustrate prior approaches to the solution of this problem. Fackler et al, in, "Light Emitting Diode Editing Display" IBM TDB, Vol. 22 No. 7 December 1979, pp2614-16 illustrates how two rows of vibrating LED's may be used to display a fully readable single line of text and an associated image of a full page of text displayed at a resolution inadequate for resolution of each character but adequate for format presentation. Other suggestions directed at CRT displays are Bringol, "Abbreviated Character Font Display", IBM TDB, Vol. 19 No. 9 February 1977 pp3248-49; Webb, "Combination of Alphanumeric and Formatting Data on CRT Display" IBM TDB Vol. 15. No. 7, page 2136 December 1972 and Lindsay, "Segmented Display" IBM TDB, Vol. 14 No. 5 October 1971, pp1528-29. Bringol illustrates a new font which can give a viewer quick access to a particular portion of a page without actually displaying text. Webb illustrates a CRT display which, in addition to displaying a few (3) lines or line portions of text simultaneously displays format information to locate the displayed line portions. Finally, Lindsey shows how a display of 40-70 characters in length can be used to access various line segments as selected by an operator for editing.
In addition, U.S. Pat. No. 4,168,489 discloses Full Page Mode System for Certain Word Processing Devices which allows a full page of text to be displayed on a 10.times.5 inch screen which is generally considered too small for displaying a full page of text. This is accomplished by displaying only five of the fourteen dot rows per character vertically and reducing the current to the CRT horizontal deflection circuit by a factor of three by switching an inductor into the deflection circuit. See also Haak U.S. Pat. No. 4,230,974. The assignee of U.S. Pat. No. 4,168,489 announced a video type 1000 which has one mode of display with a 23 line capacity, but has another mode for displaying 66 lines on the same 10.times.5 inch CRT.
It is thus one object of the present invention to provide a display which is of the size normally associated with less than full page displays, but which is capable of giving the operator an accurate preview of what the printer would produce.
Commercially available electronic displays and components can be arrayed in a spectrum of relatively simple devices having relatively limited resolution, up to more complex, bigger and more expensive devices with increasing resolution. At the lower end of the spectrum is a standard TV set and a standard TV monitor, which is identical to a standard TV set with the radio frequency circuitry eliminated. As is well known to those skilled in the art, characters can be displayed on an ordinary cathode ray tube screen by employing coded signals each character being associated with a different code. A character generator is provided which responds to different codes and generates video signals capable of causing a dot-like image of associated characters to be displayed. Commercially available componentry includes video control integrated circuits for controlling the interaction of such a character generator, and horizontal and vertical synchronizing signals to convert a string of coded signals representing characters into a video signal which, when displayed on a cathode ray tube will portray a visible image comprising a sequence of the characters corresponding to the sequence of coded signals. The commercially available integrated circuits are, however, configured to be compatible with the resolution of standard TV sets, so that the number of characters per line and number of lines per screen is limited to less than the number of character spaces per typical line of text, and less than the number of typical lines per page. It is another object of the present invention to enable the foregoing capability, i.e., that of giving the operator the benefit of a full page preview from an electronic display whose area is inadequate to display a full page of text with adequate resolution, and to achieve this object using commercially available cathode ray tube integrated circuits (chips).
Present day technology allows the operator to change format of existing text by altering margins relative to page boundaries. However, it is also desirable to allow the operator to alter the relationship of the text to existing page boundaries without altering the format of the text relative to itself.
In order to assist the operator in editing functions the display, in one mode, shows both tab and indent tab function locations via unique graphics. Other functions, e.g., carrier returns (CR) temporary left or right margin (TL,TR) are not displayed unless the cursor is positioned to overlie such functions. At that time, the function is displayed via further unique graphics.
In the same mode of display since less than a full page of text is displayed the machine supports scrolling. To maintain contextual reference, however, scrolling (vertically only) breaks screen displays at convenient paragraph or sentence boundaries, if possible.
In one mode (unformatted) of display, the unnecessary word spaces on the display are created for display convenience and have no real existence relative to the document being created or edited. Accordingly, the cursor controls prevent the cursor from being located in any area not occupied by text and/or functions.
In another mode (formatted) of display a novel hyphenation function is supported which shows the operator information respecting not only the hyphenation candidate in its relation to the right margin but also its relation to the average preceding line ending. This allows greater uniformity in line endings without the necessity for justification.
In order to further assist operator formatting decisions, on request the display will indicate the right and left margins and tab grid. Since these parameters may well vary within a document the actual locations identified for these parameters is dependent on cursor location.
Contrary to the unformatted display, in the formatted display non-text filled locations have a real existence and therefore the cursor controls allow the cursor to be positioned within or without the text filled area. Performing an insert function to a document location outside of existing text produces a text matrix having special attributes. For one thing such text matrix (termed a block) can be treated as an entity separate and apart from the document text. It can be moved in a simple fashion relative to other document text or deleted, for example.
To produce the formatted and unformatted displays the processor uses the same basic document but applies different rules in creating the display. The former display is created by observing constraints imposed on the document by margins, indents, tabs, etc. In addition, the specific effect of any of these constraints can be varied under operator control. To achieve the effect of a full page formatted display without the necessary resolution to distinguish each display character, the display provides resolution sufficient to resolve only printable character/graphic filled locations from unfilled locations, i.e., each printable character or graphic is treated and displayed identically. On the other hand, the unformatted display simply extracts a string of text characters or punctuation graphics and strings them along, breaking lines substantially only when display capacity is reached i.e., margin effects are not displayed as such.
Finally, using high rate digital signals in connection with CRT's whose phosphors were not designed for such signals can produce an effect termed "blooming" i.e., the image actually displayed is increased in size as a consequence of the interaction between CRT characteristics and the particular driving signal. By use of appropriate logic to monitor the video signal along with signal shaping the effect of "blooming" can be controlled.